Abstract

In today’s challenging market conditions, the probability of successful well delivery can be increased and influenced by implementing fit-for-purpose pre-drill and real-time geomechanical solutions. These tailored geomechanical solutions add value to the project by delivering a cost-effective well, with reduced non-productive time (NPT), and a lower risk of health, safety, and environment (HSE) concerns. Geomechanics guided decision making, both in the pre-drill and in the real time phases, has a wide range of applications depending on the complexity present in the drilling environment, e.g., high-pressure, high-temperature (HPHT) regimes, reactive clays, depleted reservoirs, weak shales, highly stressed areas, etc.

This paper discusses the application of advanced geomechanics in three specific drilling environments (a) drilling a highly deviated well in a transitional fault regime, onshore the Nile Delta, (b) mitigating wellbore instability caused by reactive shales, in the Middle East and (c) drilling lateral wells in a highly-stressed carbonate formation. The paper also discusses how integrated pre-drill and real-time geomechanical solutions helped in achieving drilling success without adding major cost to the project.

In study (a) the operator had successfully drilled many vertical wells in the onshore field on the Nile Delta without significant problems, yet was having severe issues drilling deviated wells. A detailed pre-drill model revealed the possibility of a transitional faulting regime, in association with anisotropic rocks, drilled by a slick Bottom Hole Assembly (BHA), could be a major reason for this. Real-time geomechanics were deployed to validate the pre-drill understanding, along with mud additive recommendations and a slight modification to the drill string. In a different study (b) performed in another onshore Middle East field, there was a challenge to drill high-angle wells through troublesome shale formations, which resulted in various sidetracks and a significant amount of wellbore instability issues. These issues limited well configuration options for field development to near vertical wells. A pre-drill geomechanical study was carried out to understand the root cause of the failures that resulted in customized mud weight and mud type solutions for drilling higher angle wells. With these customized recommendations and later on a 3D Geomechanical model, horizontal wells have been drilled successfully for optimal draining of the reservoir resulting in breakthrough in field development plan. In study (c) there was significant wellbore instability challenges while drilling lateral wells through highly-stressed carbonate reservoir. A comprehensive study helped in understanding the geomechanical behavior. In example highlighted the drilling team was using lower than required mud weights in a horizontal well. The geomechanical model was adjusted considering time and space for specific case using the geomechanical understanding. The focused geomechanical modeling helped to adjust the mud weight. Suitable mud weight along with pseudo real-time monitoring helped in successful delivery of the horizontal well.

The three studies presented are onshore. Conventional wisdom for onshore drilling has a bias for low-cost solutions. However, the complexity of each drilling campaign was different. In all the cases the adoption of integrated geomechanics through the planning and operation phase ensured successful project completion with minimal non-productive time (NPT).

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